3 2 1
0 -1 -2 -3
Figure 2a: Overall user satisfaction
given the building’s success at attracting public events in the central atrium, which can be perceived as disruptive to office users when the general background is very quiet.
Feedback on overall comfort, including air temperature and perception of ‘freshness’, is very positive. Summer conditions are rated particularly well, with overall comfort (taking account of temperature, air quality, and air movement) in the top 20% of BUS- surveyed buildings (Figures 3a, 3b and 3c). Comfort will be monitored if occupancy and equipment levels increase, but it is currently a success of the architectural and environmental strategy, achieved with little mechanical ventilation and with cooling in only three spaces, and in contrast with the tendency of modern offices to overheat.
Controls While users are overall satisfied with environmental conditions, they have expressed a desire for more control over their surroundings, particularly lighting. This is a recurrent design dilemma between automated and manual controls when trying to create comfortable environmental conditions while limiting energy consumption. A review of these results with the university concluded that future design briefs would likely keep the same limited level of user control on heating, ventilation, and cooling, but would aim to provide a higher level of manual control over lighting.
Energy Energy consumption data was gathered quarterly over a two-year period and compared with industry benchmarks (CIBSE Guide F). In order to make an appropriate comparison, an average of
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Naturally Ventilated Open Plan Office and Higher Education Sciences Lecture Room benchmarks were used. As the building receives hot and chilled
water from the campus energy scheme, notional consumption figures for gas (for heating) and electricity (for cooling) were derived from the meter readings of heating and cooling received from the energy scheme. It should be noted that this study focused on the performance of the building itself, without taking account of the university’s district CHP scheme. The CO2 savings offered by CHP are therefore not reflected in the analysis. Heating consumption levels are
good, being 20% below ‘Good Practice’ benchmarks and 50% below ‘Typical’ benchmarks. Electricity consumption is approx 50% above ‘Good Practice’ benchmarks and 10% above ‘Typical’ benchmarks (Figure 4). This pattern is representative of modern buildings, which tend to have good insulation and air tightness levels, but higher equipment levels than was the case when industry benchmarks were gathered. This can also be explained by the specific characteristics of the Digital Lab, including some high electricity consumption items as part of research activities, and the fact that the building is open 24/7. The comparison nonetheless reinforces the fact that CIBSE Guide F benchmarks, widely used in the industry, are still robust energy demand prediction tools. Part L model results are available for
the building, but these are meant as a Building Regulations compliance tool using theoretical set assumptions, and are therefore not appropriate to compare with actual energy use. Electricity for cooling represents
only a very small part of overall energy Uncomfortable :1 Tsover Figure 3a: Overall summer comfort Too hot :1 Tshot Figure 3b: Summer temperature Unsatisfactory :1 Airsover Figure 3c: Air in summer
Figure 3: User satisfaction survey (BUS methodology). Green squares show where average scores are significantly better than benchmark; the orange circle indicates averages that are similar
7: Satisfactory 7: Too cold 7: Comfortable
Bussatindex Poor Image :1 Figure 2b: Image to visitors 7: Good
Percentile
Very poorly :1 Workreq Figure 2c: Do facilities meet needs?
7: Very well
The post-occupancy evaluation of the Digital Lab has highlighted a number of lessons that should be valuable for the university’s future buildings and for designers of buildings with low carbon aspirations
April 2012 CIBSE Journal 27
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